Fokker's
"Eindecker" was the first monoplane fighter in WWI,
but it was also the first to be able to fire a forward facing machinegun
through the propeller without having the bullets hit it. Previous
designs on both sides allowed firing through the propeller only with
deflectors mounted on it that did not always deflect the bullets, and
still put considerable stress on the wooden propeller. This synchronized
firing mechanism was a major step forward in aerial combat, as it
avoided damaging or stressing the propeller and allowed the pilot to
fire the gun at an opponent simply by pointing his aircraft at
it.
For a few
months in early 1915 the Eindecker destroyed the Allies superiority in
the air during the Fokker Scourge. The aircraft was used in large part
to prohibit Allied access to German airspace, as the pilots were
instructed not to dogfight over Allied territory for fear of having the
synchronizing gear fall into enemy hands. The monoplane was used to
control the air over Verdun during their offensive of Feb. 1916. By
summer of 1916 the Allies regained aerial superiority with other
aircraft.